1. Field
The present disclosure relates to a genetically engineered and stress resistant yeast cell with enhanced MSN2 activity and a method of producing lactate using the same.
2. Description of the Related Art
Organic acids are extensively used in industrial fields. For example, lactate is an organic acid which is widely used in various industries such as the food, pharmaceutical, chemical, and electronic industries. Lactate is a colorless, odorless, and highly water-soluble substance having low volatility. As lactate is nontoxic to the human body, lactate is used as a flavoring agent, an acidifier, and a preservative. In addition, lactate is a raw material of polylactic acid (PLA), which is an environment-friendly alternative polymer substance and a biodegradable plastic.
An organic acid is separated into a hydrogen ion and an anion of the organic acid under pH conditions higher than a pKa value of the organic acid, for example, under neutral conditions. However, an organic acid, for example, lactate, exists as a free acid having no electromagnetic force under conditions wherein the pH is lower than the pKa value of the organic acid. Since an anion form may not penetrate a cell membrane, while a free acid form may penetrate a cell membrane, an organic acid outside a cell membrane may be introduced to the inside of a cell in an environment where a concentration of an organic acid is high, and thus an intracellular pH may be decreased. In addition, an organic acid in the form of an anion existing under conditions where the acidity is higher than the pKa value of the organic acid exists in the form of a salt during cell culturing or fermentation by adding a salt such as a neutralizing agent, and then the organic acid is separated from the produced salt form. As a result, a cell lacking acid resistance may lose cellular activity under acidic conditions including lactate and then die.
Therefore, there is a need for not only a microorganism having acid resistance but also a microorganism that is resistant to stresses such as osmotic pressure.